PASADENA, Calif. -- Mario Van Peebles has a simple theory about playing a real person: "You want to know as much as possible, I think, then forget it and be it." He's had plenty of experience lately. He portrayed 19th century poet Paul Laurence Dunbar in the play "Oak and Ivy" at the Vineyard Playhouse in Martha's Vineyard last summer. He appears as Malcolm X in the current movie "Ali." And now, in Showtime's "10,000 Black Men Named George," he plays Ashley Totten, one of the founding members of the Brotherhood of Sleeping Car Porters.